Thermo-responsive switch



p 2 1959 J. SCHMIDINGER 2,906,835

mauo-ansponsxvs swncn Filed July 12, 1956 2 Sheets-Sheet 1 I N V EN TOR.Mast/w Scx/u/o/zvem BY g 111m 1.6m

ATTORNEYS Sept. 29, 1959 J. SCHMIDINGER 2,905,335

Tl-IERMO-RESPONSIVE SWITCH Filed July 12, 1956 2 Sheets-Sheet 2 /00' 665do 3 76 2 (f3 /dza /02 /d/ /00 949 )50 W26 90 ATTORNEYS United StatesPatent THERMO-RESPONSIVE SWITCH Joseph Schmidinger, Lake George, NY.

Application July 12, 1956, Serial No. 597,502

14 Claims. (Cl. 200-88) The present invention relates tothermoresponsive switches of the type wherein expansion and contractionof flexible wires or strips with passage of current therethrough actuatecircuit controlling contacts and comprises a novel switch of this typewhich has a number of advantageous features. In the new switch allinsulated anchorages, such as glass beads, clamped or riveted plates orthe like, for the pull wire or strip are eliminated, perrnitting thepull wire or strip to be connected under tension between strong metallicparts of the same electrical polarity, thus insuring against any loss ofthe critically adjusted tensions of the pull means often caused bymechanieal failure of such insulated tension anchorages. Also in the newswitch, the pull wire or pull strip is connected in series-parallelwhich permits the use of a much thinner pull strip per given currentthrough the device as compared to devices of this character wherein thepull strip or wire is connected in straight series with the load currentthrough the device. The pull strip, being thinner, heats and cools morerapidly and thus faster starting and operating speeds are obtained. Alsoin the new switch when used, for example as a series lamp signalflasher, required starting and operating speeds can be obtained atsubstantially lower terminal resistance as compared to devices which usestraight series connected pull means for operating contacts.Furthermore, in the preferred embodiment of the invention wherein theswitch is electromagnetically controlled, the contacts are so positionedand arranged as to be broken in a collapsing magnetic field, therebyinsuring magnetic spark quenching The new switch comprises a contactcarrying member biased into one circuit controlling position and a pullstrip secured at its ends to metal parts of the same polarity, holding,when cold or cool, the contact carrying mcrnber in another circuitcontrolling position against the bias thereof, an electrical conductorbeing connected to the pull strip intermediate its ends. In theelectromagnetically controlled switch the contact carrying member is anarmature of an electromagnet, one end of the winding of which isconnected to a point of the pull strip intermediate its ends. Thus Whena circuit includinga load and a so rce of ener y i on e e a s the h r ndof the winding n a n a P iii r engagement hen the arm ture is i a a e pon u re t W l 19W #9 opposite directions through the parts of the pullstrip betwee its a cho e ends a d t p n tt c me t o the el t c on uct Tcon eque at n and expansion of the pull strip permits the armature to'move to re act d P n de the enc of a S ng QPshing the circuit of thecoil and pull strip. Upon cooling and contraction of the wire thecontacts are again closed and th cy e pea T Switch m d i n d for use asan overload circuit breaker, as a flasher or as a relay. It requires butfew and simple parts and is of sturdy co stru i Eo a et e u der ta di ofh vs ihn e e n ma e a t the accompanying d aw n s. f h ch figs and 2 a ede nd 212 .1 vi ws rss ss vs y 9 e1 ice electromagnetically operatedswitch embodying the inv ntio Fig. 3 is a transverse vertical section ofthe switch of Figs 1 and 2 taken on the line 33 of Fig. 2;

Fig. 4 is an exploded view of certain of the parts of the switch ofFigs, 1 to 3, showing the mounting of one of the stationary contacts;

Fig. 5 is a circuit diagram illustrating use of the switch of Figs. 1 to3 as a circuit breaker or flasher;

Fig. 6 is a vertical sectional view of a switch of the sprung vane typerepresenting another embodiment of the invention;

Fig. 7 is a transverse sectional view taken on the line 7-:7 of Fig. 6;and

Fig. 8 is a longitudinal sectional view, partly in eleva: tion of aswitch having a snap plate and representing still another embodiment ofthe invention.

In the embodiment of the invention illustrated in Figs.

1 to 3, the parts are mounted on a base 2 of insulating material to theunder surface of which three terminal prongs 4, 6 and S are secured byrivets 10, 12 and 14 espectively. The base 2 is thicker at one end thanat the other to provide a shelf or platform 16 to which is secured bythe rivet 14 one end of a magnetizable plate 18. The other. end of theplate 13 is cut away to provide a generally L-shaped member about thelong arrn'lSa of which is wound the coil 20 of the electromagnet, and tothe short arm 18:) of which is secured one arm of an L-shaped leafspring 22. An armature 24 of the electromagnet is secured to the spring22, which latter biases the armature toward retracted position. Theplate 18 has an upwardly extending portion at the anchored end of theplate, and to the upper end of this upwardly projecting part is firmlysecured, as by welding, one end of a pull strip 26, the other end ofwhich is similarly anchored to the free end of the spring 22. Thetension in the pull strip 26, when the strip is cold or cool, is such asto hold the armature 24 in attracted position. The initial tension inthe strip can be adjusted by bending the part 18c about its junctionwith the plate 18. A metallic plate 28 is insulatedly mounted on theanchored portion of plate 18 by means of rivet 14, a sheet 30 ofinsulating material, for example of mica, being positioned between theplates 18 and 23. A tongue 28a formed by slotting the piate 28 andupward bending of the metal between the slots carries a contact '32positioned for engagement by a contact 34 carried on the'underside ofthe armature 24. Adjustment of the spacing of the contacts can thus bereadily effected by adjustment of the tongue 28a toward and away fromthe plane of the plate One end of the winding 29 is connected to theterminal 4 by means of the rivet 1S, and the other end of the Winding 20is connected by a short conductor 35 to the pull strip 26 intermediatethe anchored ends thereof. Preferably, in order to provide for thecircuit of a pilot lamp, a bracket 36 which is supported on the base 2by means of the rivet 12, has a part 38 extending over the armature 2.4and positioned to be engaged thereby when the armature moves toretracted position.

The above described thermo-responsive switch is made of relatively fewand simple parts. The pull strip 26 is anchored directly on strong metalparts, the projection 18c at one end and the spring 22 at the other, andthe only insulation necessary for the whole device is that provided bythe base Stand by the insulating sheet 30 which insulates the plate 18from plate 28.

Fig. 5 illustrates diagrammatically the operation .of the device incontrol of a lamp circuit. In the circuit of Fig. 5 terminal 8 isconnected to the load, which in this particular instance comprises apair of lamps 40 connsstsd Pa alle between te mina 8 d sn hn Thetsraiiesl 4 o t e d i e is squash d t rs s a suit:

a pilot lamp 46 to ground. With this circuit, when switch.

42 is open and the pull strip accordingly cold, contacts 34 and 32 arein engagement, but no current flows through the winding 20. Upon closureof the switch, current flows through the winding 20 through two parts ofthe strip 26 in opposite directions, through the plate 18,

armature 24, and contacts 34 and 32 to terminal 8 and thence through thelamps 4-0 to ground.

The tension in the pull strip 26 opposing spring 22 is thus reinforcedby the magnetic attraction of the armature and firm contact'pressure isinsured. Assuming that the device is designed to operate as an overloadcircuit breaker, then the expansion of the pull strip under normalcurrent therethrough will not be suffici'ent top ermit opening of thecontacts by the spring 22. Upon a sudden increase in current, however,over and above the normal current, the tension in the pull strip due tothe excessive heating current will reduce to an extent sutficient topermit spring 22 to retract the armature 24, thereby opening the circuitat the contacts 32 and 34. The opening of the circuit collapses themagnetic field and thereby provides magnetic spark quenching at thecontacts. Opening of the contacts and retraction of the armature closesthe circuit through bracket 36 and the armature 24 to the pilot lamp 46which thereupon lights to indicate that the circuit of the lamp load hasbeen opened. Upon consequent cooling and contraction of the pull strip26 the armature is again brought into attracted position, closing thecircuit and again energizing the lamps 40. If the cause for theexcessive current still remains, the cycle will repeat. For operation asa flasher, the dimensions of the pull strip are such as to cause openingof the circuit under normal current conditions.

Figs. 6 and 7 illustrate a non-magnetic type of thermoresponsive switchembodying the invention. The switch of Figs. 6 and 7 is of the sprungvane type disclosed and claimed in various prior patents of the presentapplicant. (See, for example, Schmidinger Patents 2,074,345, dated March23, 1937; 2,133,309, dated October 18, 1938; 2,299,767, dated October27, 1942; and 2,388,712, dated November 13, 1945.) The construction ofthe new sprung vane type switch is substantially simpler than that ofany one of the above mentioned patents and differs from the patenteddevices in various respects and spe cifically in that the pull strip isfirmly anchored at each end to metal parts of the same electricalpolarity.

The simple switch of Figs. 6 and 7 comprises a clamping channel frame 48provided with an insulating lining 50 and with an opening 52 in its wallfor accommodation of a contact 54 carried by a sprung vane 56. The vane56 is anchored at each end on the frame 48 at points spaced apart adistance less than the length of the vane to cause the vane to assumethe buckled position indiaeoasse lining to provide a second terminal forthe switch, the first terminal being the plate 64. Plate 68 is connectedby a conductor 70 with an intermediate point on the pull strip 58. Plate64 can be connected to a source of energy, as for example a battery 72,and plate 68 can be connected through a load to the other terminal ofthe battery 72, as for example'thro'ugh the load comprising lamps 74.

The operation of the above described switch will be readily apparent.When no current flows through the device, as for example when a switch76 in the line connecting plate 64 with the battery 72 is open, thetension in the pull strip 58 maintains the contacts 54 and 66 inengagement. Upon closure of the switch, current will fiow from thebattery through the contacts, sprung vane 56 and from both ends of thepull strip to the part 70, plate 68, and the lamp load 74 backlto thebattery to energize the lamps. Upon heating and consequent expansion ofthe pull strip, the tension in the pullstrip will be reducedsufficiently to permit the vane to spring into the dotted line position,thereby opening the circuit .at contacts 54 and 66. The pull strip willthereupon cool and contract and return the vane to contact closingposition. Thus the device operates either as anoverload circuit breakeror flasher, depending upon the initial adjustment of the tension in thepull strip and :upon the particular dimensions of the pull strip. Theprojecting arm 69 of the frame provides ready means for adjustment ofthe tension of the pull strip and the extension of the plate 64 issuingfrom the frame provides ready means for adjustment of the positionofstationa ry contact 66. The device thus comprises essentially buteight parts. These are the channelframe member 48, with its insulatinglining 58; the two terminal members 64 and 68; the sprung vane 56; thepull strip 58 with its anchor 62; and the conductor 70. By connectingthe pull strip at a point intermediate its length to a terminal of theswitch, insulated anchorages for the pull strip are eliminated,facilitating mass production and reducing the number of rejectsordinarily encountered in the manufacture of devices of this type. Theswitch may be made of relatively small dimensions and is sturdy withfew, if any parts subject to wear.

In each of the embodiments of the invention so far described, thepullstrip, when cold, maintains contacts closed and when heated by passageof current therethrough permits movement of the contact carrying memberto circuit opening position; The devices are thus suitable for use asflashers or overload protectors. In the embodiment of the inventionillustrated in Fig. 8 and I "now to be described the contact carryingmember, when cated in dotted linesin Fig. 6. A pull strip 58 is firmlyanchored at one end to a metallic and bendable projection of the frame48 and at its other end to one leg 'carries a contact 66 positioned forengagement by the contact 547when the vane is in buckled position intowhich it is constrained by the pull strip 58. The plate 64 beyond thestationary contact 66 is bent downwardly and extends beyond the sidewalls of the channel to provide a means for adjustment of the positionof the sta tionary contact. A second conducting plate 68 is insertedinto the other end of the frame 48 within the insulating the pull stripexpands, closes an auxiliary circuit, the main circuit including thepull strip being independent of the position of the contact carryingmember. Thus the device operates essentially as a relay.

In Fig. 8, the contact carrying member indicatedgenerally at 78, is asnap plate of the construction described and claimed in applicantscopending application Serial No. 347,380, filed April 7, 1953, andentitled -Wire Controlled Snap Switch (now Patent No.-2,76l,931). Itcomprises three metal strips interconnected at their ends, the outerstrips 79 being co-planar and the inner.

strip 80 being biased at its ends to bow outwardly from the plane of theouter strips. The plate 78 is fixedly mounted at one end. The other end,which carries an electrical contact 81 on its under side and aninsulating button 82 on its upper side, is free to move between fixedstops 83 and 8 4, the latter of which is an electrical contact. An anglemember 86 is mounted'on the central strip 80 adjacent the fixed end ofthe plate and re the angle member 86 is secured under tension one end ofa pull strip 88. The tension applied to the pull strip, whether expandedas a result of passage of current there through or contracted when cold,is suflicient'to cause the'central unbiased portion of the inner strip80 to flex oppositely tothe biased ends thereof so that the centralstrip assumes the shape of a relatively fiat M, all as, described in:the said copendingapplication Serial No. 347,380. In. accordance withthe present invention a metal. frame member 90 of U cross section has.its side walls turned inwardly to clamp therewithin two flat, conductors92 and 94. which are insulated from the walls of the frame member 90 byasheet 96 of insulating ma. terial folded around the conductors duringthe clamping operation. Conductor 92 extends from beyond one end of themember 90 to about the central portion thereof where-it terminates in araised shoulder 92a upon which is; mounted the contact or stop 84, and atail portion 92b generally perpendicular to the member 90 and protrudingout therefrom through the space between the turned inside walls. Theshoulder portion 92a is disposedv within an opening 90a in the upperwall of the frame member. Conductor 94 extends from the. neighborhood ofopening 90a to and beyond the other end of member 90 to provide oneterminal of the device, specifically shown as a grounded terminal. Thesnap plate 78 is mounted on a step 98 which is a projection of thecopper wall of frame member 90 and which is extended beyond the body ofthe frame member to provide a second terminal 100 of the device. Stop 83comprises a button. mounted on the underside ofan overhanging arm102'aof a generally hook shaped member 102. Member 102 has a shank portion102b which extends through the opening 90a in the member 90 and iswelded to the tail portion 92b of. conductor 92, permitting conjoint adjustrnent of the position of the stop members. Frame member 90 at the endremote from the terminal 100, has a bendable extension 104 which isturned upwardly and to the upper end of which is secured under tensionthe other end of the pull strip 88. Thus both ends of the pull strip aremechanically and electrically connected to the frame member 90.Conductor 94 is connected by a flexible lead 106 to the mid point of thepull strip.

In Fig. 8 the snap plate 78 is shown in the position to which it isbiased by maximum tension in the pull strip 88, that is with theinsulator button 82 on the free end thereof in engagement with thebutton or stop 83. Whenthepull strip expands the amplitude of curvatureof the portions of the central strip 80 reduces causing the free end ofthe snap plate to move away from stop 83 and snap into position wherecontact 81 engages contact 84. For a more complete description of theoperation of a snap plate of the general type of plate 78 of Fig. 8 andof its operation during change in tension of the pull strip or wire,reference may be had to the said copending application.

Terminal 100 is connected through a lamp load, comprising three lamps108 in parallel, and a control switch 110 to the positive terminal of abattery 112, the negative terminal of which is grounded. Conductor 92 isconnected through a pilot lamp 114 to ground. Thus when switch 110 isclosed current flows from the positive terminal of the battery, throughthe lamps 108 in parallel, to terminal 100 and frame member 90, fromboth ends of frame member 90 through the halves of the pull strip inparallel to the conductor 106, conductor 94 and ground. The consequentexpansion of pull strip 88 causes plate 78 to snap into position whereinthe contact 81 engages contact 84 thus closing a circuit through thesnap plate, conductor 92 and pilot lamp 114 to ground. The parts willremain in this position so long as all lamps 108 are functioning andcarrying their respective share of the current. Upon failure of one ormore of the lamps 108 and consequent reduction of current through thepull strip, the strip will contract and cause plate 78 to snap intoposition to open the circuit through the pilot lamp. Thus the currentthrough the auxiliary circuit including the pilot lamp is controlled bythe switch whereas, in contradistinction to the embodiments of theinvention illus- 6 ttated in. Figs. 1 to. 7, the circuit of the pullstrip is not dependent upon the position of the contact carrying member.The. particular circuit, shown in Fig. 8 is typical of any one of manycircuits which might be advantageously controlled by the switch of Fig.8.

The invention has now been described with reference to three specific.embodiments, thereof in each of which a pull strip is anchored. at bothends to metallic members of the same electrical polarity. In two of theembodiments the pull strip, when cold, maintains contacts in closedposition, the pull strip when heated by passage of current therethroughpermitting spring means to open the contacts. In the, third embodimentthe pull strip when cold maintains. contacts, in an auxiliary circuitopen and when heated by passage of current therethrough permits springmeans to close the contacts of the auxiliary circuit. In the.electromagnetic thermo switch of one embodiment of the. inventionmagnetic spark quenching is provided. Obviously, various changes in thespecific constructions illustrated could be made without departing fromthe spirit of the invention or the scope of the accompanying claims.

This application is a continuation-in-part of applicants copendingapplication Serial No. 298,385 filed luly 11, 1952 (now abandoned) andalso of applicants c0pend ing application Serial No. 347,380 filed April7, 3, now Patent No. 2,761,931.

The following is claimed:

1. A thermo-responsive switch comprising a metallic contact carryingmember movable between a first and second circuit controlling positionand biased toward said first position, a metallic structure conductivelyconnected to said member and supporting the same, an expansibleelectrically conductive pull strip mechanically and electricallyconnected at one end to said structure, means for mechanically andconductively connecting the other end of said pull strip to said memberunder tension such that when cold the strip holds said member againstthe bias thereof in said second position and when heated by pas,- sageof current therethrough permits movement of said member to said firstposition, said structure and member providing a low resistance pathbetween the ends of said strip, a fixed contact positioned forengagement by the contact carried by said member when said member is inone of said positions, and a permanent untensioned electrical connectionto a point of the pull strip intermediate its ends, whereby when saidstructure and said connection are at different electrical potentialscurrent flow in parallel through the parts of the strip on oppositesides of the electrical connection controls the position of said membercarried contact with respect to said fixed contact.

2. The thermo-responsive switch according to claim 1 wherein said fixedcontact is positioned for engagement by said member carried contact whensaid member is held by said strip in said second position, whereby whena circuit including a source of energy is connected across saidelectrical connection and said fixed contact said member will move backand forth from one position to the other as the strip expands andcontracts.

3. The thermo-responsive switch according to claim 1 .Wherein said fixedcontact is positioned for engagement by said member carried contact whensaid member is in said first position, whereby when a first circuitincluding a source of energy is connected across said structure and saidconnection and a second circuit is connected across said contacts, saidsecond circuit may be opened or closed at said contacts by control ofcurrent in said first circuit.

4. A thermo-respcnsive switch comprising a metallic contact-carryingmovable member, a fixed contact positioned for engagement by the contactcarried by said member when said member is in one position, said memberbeing biased toward a non-contact engaging position, a metallicstructure conductively connected to said member, an expansibleelectrically conductive pull strip mechanically and electricallyconnected at one end'to said structure, means for mechanically andconductively connecting the other end of said pull strip to said memberunder tension such that when cold the strip holds said member in saidcontact engaging position and when heated by passage of currenttherethrough permits movement of said member to said non-contactengaging position, and an electrical connection to a point of the pullstrip intermediate its ends whereby, when said strip is cold and acircuit including a source of energy is connected across said connectionand said fixed contact, current flows in parallel through the parts ofthe strip on opposite sides of the electrical connection, through saidstructure and member to said fixed contact.

5. The switch according to claim 4 wherein said member is an armature ofan electromagnet and is spring jhias'ed into retracted position, saidstrip when tensioned holding said armature in attracted position, andwherein one end of the. winding of the electromagnet is connected tosaid strip.

. 6. The switch according to claim 5 wherein said fixed contact isinsulatedly mounted on the core of said elec tromagnet to providemagnetic spark quenching upon opening of said contacts.

7. The switch according to claim 4 wherein said contact carrying memberis a vane having an inherent constraint therein tending to move it intocontact open position, said strip when under tension buckling the vaneto contact closing position.

8. A thermo-responsive electromagnetic switch comprising a core ofmagnetically permeable material, a winding on said core, an armaturespring-mounted on said core so as to be biased into retracted position,a

tensioned strip of electrically conducting material secured at one endto said armature and at its other end to said core, the tension in saidstrip'opposing the spring bias of said armature, a contact insulatedlymounted on said core and positioned for engagement with said armature inattracted position, an electrical connection .between one end of saidwinding and. a point on said adjustment of the angle of said portionrelative to the face of the sheet.

7 10. The switch according to claim 9 including a sheet of insulatingmaterial overlying a part of said core, and

a metallic plate overlying said sheet and having a tongue pressedoutwardly therefrom, said contact being mounted on said tongue and beingadjustable relative to said armature by adjustment of the position ofsaid tongue.

11. The switch according to claim 8 including a base of. insulatingmaterial, said core and said terminals being mounted on said base, athird terminal mounted on the base, a fixed contact supported from saidbase and positioned for engagement with said armature in retractedposition, said last mentioned contact being electrically connected tosaid third terminal.

12. A thermo-responsive switch comprising a metallic channel memberclosed, along three sides, an insulating sleeve within said member,conducting members clamped in said sleeve at each end of said member andextending outwardly therefrom, said member and sleeve having alignedopenings therein, ,a vane secured at its ends under compression tosaidlmember so as to be constrained into a bowed position, a,thermo-expansible'pull strip secured under tension at one end to saidvane and at its other end to said member, the tension in said pull stripbuckling said vane in opposition to the constraint therein, acontactlcarried by said vane and positioned in alignment with saidaperture, a contact carried within 'said channel member by one of saidconducting members and positioned for engagement by said vane carriedcontact when the vane is buckled bysaid strip, and an electricalconnection between the other of said conducting members and a point onsaid strip intermediateits an.- chored ends.

13.,The thermo-responsive switch according to claim 12 wherein a portionof said contact carrying conducting member beyond the location of thecontact extends out through the open side of said channel member topro.- vide means for adjusting the position of the fixed contact.

14. The thermo-responsive switch according to claim '12 wherein saidchannel member has a portion bent outwardly to provide a tongue foranchorage of one end of said strip.

References Cited in the file of this patent UNITED STATES PATENTS1,288,947 Mclver Dec. 24, 1918 1,946,894 Brogger Feb. 13, 1934 1,967,359Hanel July 24, 1934 2,074,345 Schmidinger Mar. 23, 1937 2,172,666 MichelSept. 12, 1939 2,388,712 Schmidinger Nov. 13, 1945 2,422,077 Bucky June10, .1947 2,639,345 Sitzer May 19, 1953 2,706,226 Welsh Apr. 12, 19552,796,490 Stoltey c June 18,1957

' FOREIGN PATENTS 6,711 Netherlands Dec. 28, 1921 136,101

Great Britain Decrll, 1919

